The invention relates to a device for loading further-processing machines with printed products, in particular a feeder rack in gather-stitcher machines or gathering machines for folded sheets, sheets, booklets or the like.
Devices of this type are known as rod feeders, transfer devices, loading devices or delivery devices and are used to break up so-called rods of printed products and to transfer the printed products to a feeder rack of a further-processing machine, such as a gathering machine. For the purpose of breaking up the rod, the printed products are removed from the end face of the rod in overlapping manner, in that the horizontal rod is fed by a conveyor belt towards an upwardly sloping conveying transfer belt, where the conveying speed is greater than the feed speed of the first conveyor belt. As a result of the friction between the transfer belt and the end face of the rod, the printed products are drawn off the rod in an overlapping formation. The rod feeder can also be used to feed individual printed sheets onto the conveyor belt, thus significantly increasing the feeding capacity on the particular feeder rack.
The overlapping formation is determined by the friction ratios and is therefore dependent on the pressure ratios between the transfer belt and the end face of the rod or stack. The degree of overlap is increased as the pressure increases, i.e. the printed products are drawn off in close succession. However, if the pressure is too high, there is a risk of part stacks of printed products being drawn off or of the printed products being damaged. On the other hand, too low a pressure can result in breaks in the overlapping formation. A functionally reliable overlapping formation is desirable in that, for each printed product, the degree of overlap is approximately constant. An overlap of this type is in turn advantageous for the further transport of the overlapping stream and the transfer to the feeder rack. In order to achieve this for the overlapping formation, the feed of the rod or the stack has to correspond to the thickness of the drawn-off printed products.
In known rod feeders, the conveyer arrangements are driven by infinitely variable individual drives. The speeds are set by way of rotary potentiometers and this has to be effected by the operator setting the conveying speeds for the two conveyor arrangements as a result of observing the overlapping stream. This procedure is time-consuming, since a plurality of rod feeders can be used on a gathering machine, and it is imprecise.
The object of the invention is to provide a device for loading further-processing machines with printed products, in which the overlapping formation is effected in a functionally reliable manner and it is substantially easier to set an optimum degree of overlap.
This object is achieved according to the invention in surprisingly simple and economical manner by a control means, which sets the conveying speeds of the first conveyor arrangement (the conveyor belt for feeding the rod or stack) and the second conveyor arrangement (the transfer belt for drawing off and transferring the overlapping stream) in a ratio to one another which is dependent on the thickness of the printed products drawn off. The speed ratio is set automatically as a result of knowing this thickness. It is thus ensured that a constant degree of overlap is produced for each thickness of the printing products to be processed, in particular from the start of production. Manual adjustment of the device is reduced to a minimum.
A particularly economical device is produced if, according to a further development of the invention, the thickness of the printed products to be processed is input by way of an operating console and is thus made known to the control means. The operator determines the thickness by way of suitable measuring means. Particularly convenient operation is achieved if, according to an alternative further development, the control means has a measuring device. The control means determines the thickness automatically by way of a reference printed product. This is quick and precise. A further alternative further development provides for the thickness to be transmitted from the feeder rack to the control means by way of an electrical coupling. A thickness-checking arrangement is often found in a feeder rack of gathering machines and saddle stitching machines, it being possible to process the signals of said thickness-checking arrangement in the control means of the device. The device adjusts itself automatically to a new printed product and takes into account fluctuations in the thickness of the printed products.
The drive of the second conveyor arrangement is preferably constructed as the master which the drive of the first conveyor arrangement follows as the slave. The conveying speed of the second conveyor arrangement can thus be altered for the purpose of regulating the conveying capacity of the device, and the feed speed of the first conveyor arrangement adapts automatically to this altered conveying capacity. The conveying capacity can be regulated by hand or by appropriate control mechanisms which monitor the fill level of the rack, for example. The target values of the speed ratios for the particular thickness measurements are preferably stored in the control means. An advantageous further development provides for the speed ratio to be correctable by hand. The ratio provided by the control means for a particular thickness is thus adapted to product-specific properties (including surface of the printed products and compression of the rod or the stack).